Influence of Coexisting Fertilizers and Organic Matter on the Fate and Transport of Chlorpyrifos in Nanobiochar-Amended Porous Media

Abstract Chlorpyrifos (CPF) is a widely used organophosphate pesticide that poses environmental issues. Nanobiochar has garnered significant scientific interest because of its higher adsorption capacity. However, despite its potential for pesticide retention, the influence of biochar on CPF transport remains poorly understood. This study investigates the influence of fertilizers and organic matter on the fate and transport of CPF in nanobiochar (NBC)-amended porous media. The transport behavior of CPF in NBC-amended and unamended sand, together with the effects of humic acid and fertilizers (nitrate and phosphate), was investigated through soil column experiments. Breakthrough curves were simulated using the dual-porosity nonequilibrium model in HYDRUS-1D. The results showed that the incorporation of one percent NBC reduced C/C o from 0.45 to 0.30, indicating enhanced sorption resulting from the high surface area and microstructure of NBC. Correspondingly, the simulated sorption coefficient increased from 1.64 to 1.968 Lg −1 , indicating improved retention of CPF. Humic acid increased CPF mobility by approximately 44 percent, whereas nitrate and phosphate enhanced CPF retention by 20 percent, reducing the C/C o ratio to 0.20 in NBC-amended sand compared with 0.45 in unamended sand. The enhanced retention in the presence of fertilizers was due to electrical double-layer compression. Furthermore, pH-dependent sorption behavior indicated greater CPF retention under acidic conditions following NBC incorporation. Overall, the results demonstrate that NBC effectively reduces CPF mobility in porous media. However, its effectiveness is influenced by coexisting environmental factors. Therefore, a comprehensive investigation of additional environmental factors is required to optimize biochar-based remediation strategies.